The present invention relates generally to gas turbine engines and, more particularly, to fuel injectors used in gas turbine engines. Gas turbine engines are rotary-type combustion turbine engines built around a power core made up of a compressor, combustor and turbine, arranged in flow series with an upstream inlet and downstream exhaust. The compressor section compresses air from the inlet, which is mixed with fuel in the combustor and ignited to generate hot combustion gas. The compressor section may include a low, mid, and high pressure compressor sections. The turbine section extracts energy from the expanding combustion gas, and drives the compressor section via a common shaft. The turbine section may include a low, mid, and high pressure compressor sections. Expanded combustion products are exhausted downstream, and energy is delivered in the form of rotational energy in the shaft, reactive thrust from the exhaust, or both.
Gas turbine engines provide efficient, reliable power for a wide range of applications in aviation, transportation and industrial power generation. Small-scale gas turbine engines, such as auxiliary power units, typically utilize a one-spool design, with co-rotating compressor and turbine sections. Larger-scale combustion turbines including jet engines and industrial gas turbines (IGTs) are generally arranged into a number of coaxially nested spools. The spools operate at different pressures, temperatures and spool speeds, and may rotate in different directions.
The combustor includes a plurality of fuel injectors arranged in an annular array about a central axis of the combustor. The fuel injectors atomize and inject fuel into the combustion section of the gas turbine engine. Attached to each fuel injector is a fuel nozzle which controls the exit pattern of the fuel from the injector. Different types of fuel nozzles are used to provide different fuel flows into the combustor, examples of which may include duplex and simplex nozzles. The varying fuel flows provided by different types of nozzles cause some nozzles to burn hotter than others. The difference of combustion temperatures between the hot and cold nozzles causes a non-uniform circumferential temperature gradient throughout the engine.
The fuel injectors are typically arranged in an equally spaced symmetric array within the combustor. However, a symmetric fuel injector assembly can cause significant problems within the combustor due to the non-uniform circumferential temperature gradient. Problems often include burnout of combustor wall surfaces, decrease in combustor stability, fuel puddles, hot starts, compressor stalling, high amplitude combustion noise, limited turndown, premature wear, and high cycle fatigue cracking of structural components in the combustor, see U.S. Pat. Nos. 4,548,032 and 5,551,228; and U.S. Pat. App. No. 2012/0125006 A1. Previous attempts have been made to eliminate these problems by manipulating the pattern of fuel flowing from a symmetrical annular array of fuel nozzles to provide an asymmetrical fuel pattern across the combustor, for example, see previously discussed U.S. Pat. No. 5,551,228.